The present invention relates to a glass panel for a cathode ray tube, and more particularly, to a light-weight cathode ray tube panel having a reduced glass thickness and a high X-ray absorption coefficient.
A cathode ray tube(CRT) such as a computer monitor and television picture tube comprises three principal parts: a glass panel through which video displays may be made; a funnel which has a yoke determining the course of electron beam generated from an electron gun and is attached to the panel; and a neck equipped with the electron gun. The glass panel is required to have, among others, the strength to withstand a static stress resulting from a pressure difference between the outside atmosphere and the internal vacuum as well as the ability to shield harmful X-ray radiation below a safety regulation level.
For this reason, conventional CRT panels have remained relatively thick, entailing such disadvantages as low productivity and high material costs. Therefore, there have been attempts to develop a light-weight glass panel having a high mechanical strength and a reduced glass thickness.
For example, U.S. Pat. No. 2,991,591 suggests that the thickness of a glass panel may be reduced by imparting residual compressive stress on the face of the glass panel, e.g., by prestressing the plate in order to compensate for the static stress; and Japanese Patent Laid-Open Publication Nos. 8-138579 and 7-21944 disclose that the thickness of the face area of a glass panel may be reduced by using a similar physical strengthening method. However, the extent of thickness reduction achievable by the above methods is limited because of their inability to meet the X-ray emission specification.
Accordingly, it is a primary object of the present invention to provide a light-weight, thin panel for a cathode ray tube having a high X-ray absorption coefficient and mechanical strength.
It is another object of the present invention to provide a cathode ray tube comprising the inventive glass panel.
In accordance with the present invention, there is provided a substantially rectangular glass panel for a cathode ray tube, characterized in that the panel is made of a glass having a linear X-ray absorption coefficient of at least 34 cmxe2x88x921 at a wavelength of 0.6 xc3x85; the dimensions of the panel satisfy the condition of 0.07xe2x89xa6T/sqrt(D)xe2x89xa60.09; and the panel is prestressed so that the surface of the face of the panel has a residual compressive stress ranging from 5 to 25 MPa, wherein T is the central thickness of the face of the panel in inches and D is the maximum diagonal line length of the face of the panel in inches.